The document provides information on the basal ganglia including its history, neuroanatomy, pathways, connections, and related disorders. It describes the major structures of the basal ganglia such as the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra. It explains the direct and indirect pathways within the basal ganglia and how they regulate movement. Disorders associated with basal ganglia damage or pathology include Parkinson's disease, Huntington's disease, and Wilson's disease.

2.  Brief History and Nomenclature
 Neuro-anatomy of Basal Ganglia
 Internal Processing (Direct and Indirect pathways)
 Functional connections of Basal Ganglia
 Disorders assoc. with damage to Basal Ganglia
 Disorders assoc. with pathology of Basal Ganglia
 Summary
 References

3.  First clear identification of subcortical structures was published
by anatomist Thomas Willis in 1664.
 Basal Ganglia was then referred to as Corpus striatum.
 The term “Corpus striatum” was coined by anatomists Cecile &
Oskar Vogt.
 Detailed descriptions of Corpus straitum were given by Cajal &
Samuel Wilson.
 Substantia nigra was first described by Von Sommering.
 Subthalamic nucleus was first described by Jules Bernard Luys.

4.  By definition, Ganglion is collection of neuronal cell
bodies outside the CNS and Nuclei are collection of cell
bodies within CNS surrounded by white matter.
 So, term Basal Ganglia is a misnomer and they should
be actually called “Basal Nuclei.”
 Basal Ganglia (Nuclei) are set of deep nuclei (grey
matter) located in and around the basal part of brain
and are involved in motor control, action selection and
some forms of learning.

5.  Major Structures:
Caudate nucleus
Putamen
Globus pallidus
(Internal & External)
Subthalamic nuclei
Substantia nigra
 Other Structures:
Ventral striatum
Ventral pallidum
(also k/a Neurological or Functional classification)

6.  Striatum (Neostriatum) = Caudate nucleus + Putamen
 Corpus striatum = Caudate nucleus + Putamen + Globus pallidus
 Lentiform nucleus = Putamen + Globus pallidus

7.  Telencephalic in origin
 C-shaped structure
 Divided into 3 parts:
Head, Body andTail
 Head is continuous
with putamen
 Tail terminates in the amygdala of temporal lobe
 Assoc. with contour of lateral ventricles
(Head lies against frontal horn and tail lies against temporal horn)

8.  Telencephalic in origin
 Bounded laterally by external capsule, medially by Globus
pallidus
 Separated by Caudate by fibres of anterior limb of internal
capsule

9.  Diencephalic in origin,
also k/a Paleostriatum
or Pallidum
 Inner component of
lentiform nucleus
 Cone like structure with tip directed medially
 Bounded medially by posterior limb of internal capsule and
laterally by putamen
 Divided into external and internal segments by medial mamillary
lamina

10.  Diencephalic in origin
 Lies dorso-medially to
posterior limb of
internal capsule
 Situated dorsal to
substantia nigra
 Discrete lesions will
lead to Hemiballism

11.  Mesencephalic in origin
 It is present in mid-brain
(between tegmentum
and basis pedunculi)
 It consists of
2 components:
-Pars Compacta
-Pars Reticulata

12.  Dorsal cell rich portion
 Most of the neurons are pigmented due to the presence of
Neuromelanin
 Contains neurotransmitter Dopamine
 Contain low levels of m-RNA for DA transporter and D2 receptor
 Contains Calbindin (calcium binding protein)
 Sends projections to areas of striatum dominated by input from
limbic related structures and association regions of cerebral
cortex.
 May be associated in patho-physiology of Schizophrenia.

13.  Ventral cell sparse portion
 Uses neurotransmitter GABA
 Contains higher levels of m-RNA for DA transporter and D2
receptor
 Lacks Calbindin
 Sends axonal projections to sensori-motor regions of striatum
 May be associated in patho-physiology Parkinson’s disease

14.  Ventral Striatum: Includes nucleus accumbens, which
is the region where Putamen and Head of Caudate
nucleus fuse. It is involved in cognitive and behavioral
functions.
 Ventral Pallidum: receives afferents Ventral Striatum
and contains a group of neurons k/a Substantia
Innominata.

15.  Majority of neurons in striatum are medium spiny
neurons (medium sized 10 -20 um in diameter).
 Medium aspiny neurons, large spiny neurons and large
aspiny neurons are also found in striatum.
 In striatum, AchE-rich zones k/a matrix are surrounded
by AchE-poor zones k/a striosomes.
 Similar distribution is also found for Enkephalin,
Substance P and Somatostatin.

16.  Striatum is major recipient of inputs to Basal Ganglia
 There are 3 major afferent pathways that terminate
into the striatum:
-Cortico-striatal
-Nigro-striatal
-Thalamo-striatal

17.  Originates from all regions of neo-cortex, primarily from frontal
and parietal areas (pyramidal cells of layerV andVI)
 Uses excitatory neurotransmitter: Glutamate
 Afferents from sensori-motor cortex terminate predominantly in
the putamen whereas afferents from association regions of
cortex preferentially terminate in the caudate nucleus.
 Afferents from limbic cortex , the hippocampus and the amygdala
terminate in the ventral striatum

18.  Arises from Substantia nigra Pars compacta
 Uses neurotransmitter Dopamine
 Different portions of striatum receive input from dorsal-tier or
ventral-tier DA containing neurons of Substantia nigra.

19.  Originates in the thalamus
 The thalamic nuclei providing the projections are intra-laminar
nuclei, particularly the central median nucleus

22.  Striatum receives major projection from cerebral cortex
 Within striatum, medium spiny neurons (containing
neuropeptide Substance P) sends inhibitory projections to
Globus Pallidus internal (Gpi).

23.  Direct pathway reduces inhibitory output of Basal Ganglia
(Excitatory).
 Consequence is to promote movement.

24.  A subpopulation of these medium spiny neurons (containing
neuropeptide Enkephalin) provides inhibitory projections to
Globus pallidus external (Gpe) which sends inhibitory afferents
to Gpi.

25.  Gpe projects to Substantia nigra reticulata.
 Gpe also sends inhibitory projections to Subthalamic nucleus.
 However neurons in Subthalamic nucleus provide excitatory
projections to Gpe, Gpi and Substantia nigra reticulata.
 Indirect pathway increases inhibitory output of Basal Ganglia.
 Consequence is inhibition of movement.

26.  Dopamine released by Substantia nigra Pars Compacta:
 Stimulates direct pathway via D1 receptor.
 Inhibits indirect pathway via D2 receptor.
 Hence, Dopamine promotes movement.

27.  Gpi is the source of much of the output of Basal Ganglia.
 Gpi provides projection to the ventral lateral(VL) and ventral
anterior (VA) nuclei of thalamus and the central median nucleus
(CM).
 The substantia nigra pars reticulata also provides projections to
VL andVA nuclei.
 These projections of VA and VL project to pre-motor and pre-
frontal cortices.
 Projections of pre-motor & pre-frontal cortices project to primary
motor cortex, so Basal Ganglia are able to influence indirectly the
output of primary motor cortex.

29.  Cortical projections are to the Putamen > Gp> STN> Primary
motor, supplementary motor and Pre-motor area.
 Functions in association with cortico-spinal system to controls
complex patterns of motor activity:
-Writing, cutting paper with scissors, hammering nails
-Movements like passing a football, throwing a baseball
-Most aspects of vocalisation
- Controlled movements of eyes
Virtually any other skilled movements, most of them performed
subconsciously.

30.  Cortical projections are to the caudate.
 Most motor actions occur as consequence of sensory input and
memory; k/a Cognitive control of motor activity.
 Timing and scaling of movement

31.  Involved in motor expressions of emotions.

32.  Involved in control of saccadic eye movements

33.  Tremors
Regular oscillating movement about a joint d/t synchronous
contraction of agonist and antagonist muscles resulting from
disequilibrium between Acetylcholine and Dopamine activity in
striatum.
1. Rest Tremor: movement occurs in a relaxed supported
extremity, reduced by ambulation.
2. Postural Tremor: Sustained posture elicit tremor e.g.:
Outstretched hand
3. Intention Tremor: Active limb oscillates more prominently when
reaching target e.g.: patient trying to touch examiner’s finger.

34.  Chorea
Rapid semi-purposeful, graceful, dance like non patterened
involuntary movements involving distal or proximal muscle
groups due to involvement of caudate nucleus and degeneration
of GABA-ergic fibres.
 Dystonia
Sustained or repititive involuntary muscle contractions
frequently causing twisting movements with abnormal postures
due to lesions in putamen circuit.

35.  Athetosis
Slow, writhing, involuntary movements with a
propensity to affect arms and hands primarily due to
lesion of lenticular nucleus.
 Hemibalismus
A violent form of chorea that comprises wild, flinging,
large amplitude movements on one side of the body,
contralateral to the lesion in subthalamic nuclei.

36.  Idiopathic Parkinson’s Disease
 Huntington’s Disease
 Wilson’s Disease

37.  Neurodegenerative disease associated with loss of dopaminergic
neurons in SNPc accompained by loss of dopamine terminals in
striatum.
 Decreased dopaminergic activity on both direct and indirect
pathways will lead to difficulty in initiation of movement resulting:
 Hypokinesia, person walks slowly with little steps and stooped
posture and face looks like mask.
 Decreased activity of cortico-reticular fibres will increase tone of
muscles leading to rigidity (rigid lead pipe limb).
 Disequilibrium between Acetylcholine and Dopamine will result in
tremors.

38.  Chorea results due to damage to GABA-ergic and
Cholinergic neurons (Inhibitory pathway) that project
into the putamen which releases the inhibition resulting
in hyperkinetic choreiform movements.

39.  Autosomal recessive disorder in which mutations in the
gene atp7b, ceruloplasmin is low in blood resulting
abnormal copper accumulation in liver, basal ganglia
and other tissues.
 When cu deposits in basal ganglia esp. in lentiform
nucleus, there is cell death.
 Neurological manifestations: Tremors, Dystonia,
Rigidity, Bradykinesia, Choreoathetosis, Masked facies,
Micrographia.

40.  Major Depressive Disorder: Hyperintensities in sub-cortical
regions such as Basal ganglia, Thalamus and periventricular
regions.
 Tourette’s Disorder: Diffuse process involving CSTC
pathways.
 OCD: Traumatic and infectious lesions of Basal ganglia,
advanced studies shows metabilic abnormalities in various
circuits of basal ganglia particularly in caudate.
 ADHD: Evidence suggesting functional and anatomocal
dysfunction in frontal cortex and basal ganglia, CSTC circuit.

41.  Neuroleptic induced Parkinsonism
 Neuroleptic inducedAcute Dystonia
 Neuroleptic inducedAcute Akathisia
 Neuroleptic inducedTardive Dyskinesia
 Neuroleptic Malignant Syndrome

42.  The Basal Ganglia are a group of subcortical nuclei of
varied embryonic origin.
 Basal Ganglia includes Caudate nucleus, Putamen,
Globus pallidus, Subthalamic Nuclei and Substantia
nigra.
 Main functions of Basal ganglia are Initiation and
Execution of complex patterns of motor activity and
cognitive control of motor patterns.

43.  Abnormalities of Basal ganglia results in various
abnormal involuntary movements.
 PD, Parkinsonian syndromes, Huntington’s Disease,
Wilson’s disease are important clinical syndromes
resulting from damage to Basal ganglia.
 The importance of Basal ganglia from the Psychiatric
aspect is in the development of Neuroleptic induced
movement Disorders.

44.  Kaplan and Sadock’s ComprehensiveTextbook of
Psychiatry
 Snell’s Clinical Neuroanatomy
 Guyton and Hall’s Medical Physiology
 Lishman’s Organic Psychiatry
 Adams andVictors Principles of Neurology
 Internet, Google Scholar